This invention is directed generally to digital systems, and in particular to a technique that allows a single signal line to be used for multiple functions, including the function of detecting the presence of a unit at the receiving end of the signal line.
Today's very large scale integration techniques have achieved amazing success in implementing large amounts of function in extremely small domains. The packaging industry has followed, using such large scale integrated circuits to greatly increase the amount of function carried by or found on a circuit board, or contained in or forming a part of a sub-system, and/or a unit.
While there are a number of obvious advantages flowing from such minimization and packaging techniques, they also give rise to certain problems. One such problem the question of how to communicate with the function of such large scale integrated circuitry, boards, etc. in the sense of the signal lines needed for carrying information. For example, reducing the chip area used for the circuitry that implements the particular function or functions similarly will also reduce the periphery available for signal pins to carry signals to and from the circuitry. One solution has been to use large planar surfaces of the carrier or package containing the actual integrated circuit, but even this surface has a limited amount of room.
This problem is not limited to integrated circuit chip packages; to the contrary, the use of large scale integration can also crowd a large amount of function onto a circuit board or other sub-system package, and the problem of pin limiting is again presented.